In prior heat exchangers of the countercurrent type, the differential between the temperature of the liquid heating medium or coolant, as the case may be, and the gas or vapor discharged has been several degrees. Even in heat exchangers in which tubing in the form of several parallel pipes is provided with fins, or a pipe coil, again provided with fins, or a tube forming a series of turns in essentially the same plane and again provided with fins, the temperature differential has been unduly great. An increase in pressure, to provide a greater flow of liquid through the tube or pipe or of gas or vapor through the area around the pipe, has not sufficiently increased the heat transfer to warrant the additional pumping or blower expense. In addition, unless the unit is very large and costly, heat exchangers have not transferred heat between a liquid and a fluid, such as a gas or vapor, efficiently enough to utilize low energy differences.
Among the objects of this invention are to provide a novel heat exchanger; to provide such a heat exchanger which provides a greater efficiency, as indicated by the temperature differential between the liquid in and of the fluid out; to provide such a heat exchanger which includes a series of members through which a fluid passes; to provide such a heat exchanger in which the members are in an improved heat conducting relationship with tubing or coils through which a liquid flows; to provide such a heat exchanger which is applicable to a wide variety of uses; and to provide such a heat exchanger which is economical to construct and is effective and efficient in use.